访问超出范围Swift的变量 [英] Accessing a variable that is out of scope Swift

问题描述

我知道这是基本的东西，但我似乎无法得到这个。我有一个函数，它接受日期选择器值，将它转换为一个字符串，将它赋值给一个变量，然后它们更新一个标签文本。

我希望能够在函数外部访问该变量，以便在prepareForSegue中使用它。到目前为止，我已经尝试了一个全局变量并在函数被调用时更新它，但似乎并不奏效，并且我试图在函数中返回值，但是我必须做到这一点，因为它也没有工作。
$ b

函数：
$ b $ pre $ func datePickerChanged（datePicker：UIDatePicker） {
var dateFormatter = NSDateFormatter（）

dateFormatter.dateStyle = NSDateFormatterStyle.FullStyle
dateFormatter.timeStyle = NSDateFormatterStyle.ShortStyle

var strDate = dateFormatter。 stringFromDate（datePicker.date）
dateTimeLabel.text = strDate
}


I希望在函数中获得 strDate 。任何帮助都非常感谢！

解决方案

您可以用不同的方法来做到这一点。您可以在方法上使用inout参数允许方法更新参数，如下所示：

  var aString =
 
 func doStuffWithA （inout theString：String）{
 
 theString =Groovy
} 
 
 doStuffWithA（& aString）//将aString改为Groovy
  

或者您可以在方法外声明属性：

  class SomeClass {
 var someString：String =
 
 func doStuff（）{
 self.someString =Groovy
 
 
 
 
 
 
 $ b如果你只想要一个segue，执行SegueWithIdentifier上的对象，如下所示：
  func doStuff（）{
 
 var aString =Groovy 
 performSegueWithIdentifier（someSegue，发件人：aString）
 
} 
 
 // Th在这里你可以使用它并将它作为一个属性分配给下一个视图控制器
 
覆盖func prepareForSegue（segue：UIStoryboardSegue，sender：AnyObject？）{
 
 if segue。 identifier ==someSegue{
 
 guard让aString = sender as？ String else {
 
 return 
} 
 
让nextVC = segue.destinationViewController as！ SomeVC 
 nextVC.someProperty = aString 
} 
} 
  
 
I know the is elementary stuff but I can't seem to get this. I have a function that takes the date pickers value, converts it to a string, assigns it to a variable, and them updates a labels text.

I want to be able to access that variable outside of the function so I can use it in prepareForSegue. So far I have tried making a global variable and updating it when the function is called but that didn't seem to work, and I have tried returning the value in the function but I must have done that wrong because it didn't work either.

The Function:
func datePickerChanged(datePicker:UIDatePicker) {
    var dateFormatter = NSDateFormatter()

    dateFormatter.dateStyle = NSDateFormatterStyle.FullStyle
    dateFormatter.timeStyle = NSDateFormatterStyle.ShortStyle

    var strDate = dateFormatter.stringFromDate(datePicker.date)
    dateTimeLabel.text = strDate
}
I want to get strDate out of the function. Any help is much appreciated!
解决方案
You can do this in different ways.. You can use an inout parameter on a method to allow the method to update the parameter, like this: 
var aString = ""

func doStuffWithA(inout theString: String) {

theString = "Groovy"
}

doStuffWithA(&aString) // changes aString to "Groovy"
Or you can declare the property outside of the method:
class SomeClass {
    var someString: String = ""

    func doStuff() {
        self.someString = "Groovy"
    }
 }
If you want this just for a segue, you can pass the object on performSegueWithIdentifier, like this:
func doStuff() {

    var aString = "Groovy"
    performSegueWithIdentifier("someSegue", sender: aString)

}

// Then here you can use it and assign it as a property on the next view controller

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {

    if segue.identifier == "someSegue" {

         guard let aString = sender as? String else {

         return
         }

         let nextVC = segue.destinationViewController as! SomeVC
         nextVC.someProperty = aString
    }
}


                        
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